Matted electrodeposition coating composition and a method of producing a matted electrodeposition coating

ABSTRACT

PCT No. PCT/JP95/01021 Sec. 371 Date Jan. 17, 1996 Sec. 102(e) Date Jan. 17, 1996 PCT Filed May 29, 1995 PCT Pub. No. WO95/33795 PCT Pub. Date Dec. 14, 1995This invention offers a method of manufacturing a matted electrodeposition coating composition which does not mask the hue and the fine pattern which are inherent to the thing to be coated and also offers a method of conducting such an electrodeposition. The invention also relates to a matted electrodeposition coating composition which is characterized in containing (A) an anionic acryl resin having an acetoacetyl group in a side chain, (B) an amine and water, (C) an aldehyde and (D) an alkoxylated methylolmelamine resin with a water dilutability of not more than 4.0 cc and optionally containing (D) an acidic composition with pKa of not more than 1.9 as well as a method of producing a matted electrodeposition coating using the aforementioned composition.

TECHNICAL FIELD

The present invention relates to a formulation of a mattedelectrodeposition coating composition and a method of coating the sameand, particulary, it relates to a formulation of a colorless andtransparent matted electrodeposition coating composition havingresistances to chemicals and to weather and also to a method of coatingthe same. More particularly, it relates to a formulation of a mattedelectrodeposition coating composition having resistances to chemicalsand to weather wherein a pattern of the design due to fine unevennessand the hue inherent to the thing to be coated are not hidden but onlythe gloss on the external appearance are lowered.

PRIOR ART

Common matted coating compositions which do not hide the fine patternand the hue inherent to the thing to be coated are those in whichmicrosilica is dispersed in the coating composition. However,microsilica has a disadvantage that it is inferior in terms of aresistance to chemicals, especially to alkali, does not give a filmhaving a good transparency and affords a deposition of the microsilicaonto the thing to be coated in the case of the thing which needscomplicated coating operations whereby a difference in luster isresulted depending upon the area to be coated, especially on the upperand lower surfaces. In the meanwhile, a method of dispersing fineparticles of organic substances having small specific gravity in acoating composition has been known. For example, a product in whichorganic fine particles are dispersed in a coating composition asmentioned in Japanese Patent Kokoku No. 8975/76 is practical as a spraycoating composition of a common solvent type and a coating compositionof a dipping type although it is not suitable as an electrodepositioncoating composition. The reason is that the electrophoreticity of saidorganic fine particles is not taken into consideration at all andaccordingly that there is no property of migration in a constant ratewhen electricity is applied whereby they are detached when rinsed withwater. Further, in electrodeposition coating compositions and in coatingthe same, viscosity of the electrodeposition bath is nearly the same asthat of water in view of diffusion of generated Joule's heat andwashability with water while, in the case of the organic fine particlesmentioned in the above-mentioned patent, there is a disadvantage thatthe homogeneous dispersibility of said particles in a bath of anelectrolyte of such a low viscosity (usually containing 80-95% of water)is poor and further that no consideration is made on exclusion of thesolvent which is a cause of lowering the throwing power and of loweringthe resistane of a coated film in the electrodeposition coatingcomposition and also on exclusion of the electrolyte other than theessential components for the coating composition.

In order to overcome such disadvantages, an improvement as mentioned inthe Japanese Patent Kokai No. 141771/86 was proposed by the presentinventors. Said patent has the following advantages.

(1) Changes in gloss upon changes in electrodeposition coatingconditions, temperature of the liquid, stirring, voltage, time forapplying electricity, polar ratio, etc. are little;

(2) It is easy to make the said synthetic fine particles finer and, dueto an ionic action, dispersibility in water is stabilized;

(3) Purification of said synthetic fine particles is easy, invalidcurrent upon the electrodeposition can be prevented and no oleophilicsolvent is contained whereupon good throwing power can be maintained;and

(4) The fine particles exhibit a fluidity and are firmly present in acoated film whereupon they are not affected by washing with water.

PROBLEMS TO BE SOLVED BY THE INVENTION

Although the matted coated film prepared as such is very uniform and hasa broad operation range in each of steps of electrodeposition, washingwith water and baking, there is a tendency that, when the gloss is 20%or less (60°-mirror reflectivity), hue and pattern of the metalundercoat are hidden. Especially when the undercoat has a hue near blackcolor, such a tendency is significant whereupon the so-called metallicfeel is lost and it is sometimes judged that the external appearance isno good.

With respect to a method for preparing a matted electrodepositioncoating having a metallic feel, a method of using the microgel utilizingalkoxysilane groups as a matting means is described in the JapanesePatent Kokai Nos. 67396/84, 14281/89 and 263296/93 although they have arestriction in terms of electrodeposition coating operation such as thatgloss varies depending upon the coating conditions and that affection bythe washing step after the electrodeposition is often resulted.

MEANS TO SOLVE THE PROBLEMS

According to the present invention, the above-mentioned problems havebeen found to be solved when an anionic acryl resin containingacetoacetyl group in a side chain is neutralized/diluted/dispersed withan amine and water followed by adding an aldehyde thereto to form finegel particles which can be electrodeposited in water, said particlesbeing then compounded with an alkoxylated methylolmelamine having awater dilutability of not more than 4.0 cc as a curing agent and furthercompounded with an acidic compound with a pKa of not more than 1.9 as acatalyst for lowering the curing temperature.

Thus, the present invention provides a matted electrodeposition coatingcomposition which is characterized in containing (A) an artionic acrylresin having an acetoacetyl group in a side chain, (B) an amine andwater, (C) an aldehyde and (D) an alkoxylated methylolmelamine resinwith a water dilutability of not more than 4.0 cc and optionallycontaining (D) an acidic composition with pKa of not more than 1.9 aswell as a method of producing a matted electrodeposition coating usingthe above composition.

The matted electrodeposition coating composition of the presentinvention and a method of coating the same will be further illustratedas hereunder.

(A) The anionic acryl resin having an acetoacetyl group in a side chainis prepared either:

(1) by a method in which (a) an α,β-ethylenic unsaturated monomer havingan acetoacetyl group, (b) an α,β-ethylenic unsaturated monomer having anacidic group and (c) a monomer which is polymerizable therewith arepolmerized; or

(2) by a method in which (a) α,β-ethylenic unsaturated monomer having anacidic group, (b) α,β-ethylenic unsaturated monomer having a hydroxylgroup and (c) a monomer which is polyerizable therewith are previouslypolymerized and then (d) an acetoacetylation is carried out withdiketene or with acetoacetyl ester utilizing the hydroxyl groups in saidpolymer.

The acidic group of the acryl resin prepared by such a means isneutralized/diluted/dispersed with the amine and water and, after that,the aldehyde is added thereto whereupon, as a result of a condensationreaction of with said introduced acetoacetyl group, fine gel particleswhich can be electrodeposited in water are manufactured.

More detailed explanation will be given as hereunder.

(A)(1)(a). Representative example of the α,β-ethylenic unsaturatedmonomer having an acetoacetyl group is acetoacetoxyethyl methacrylaterepresented by the following formula 1!. ##STR1##

Besides the above, acetoacetoxyethyl acrylate, acetoacetoxypropyl(meth)acrylate, acetoacetoxybutyl (meth)acrylate, etc. are useful andderivatives prepared by a modification of hydroxyethyl (meth)acrylatewith a lactone followed by acetoacetylation may be utilized as well.

The suitable amount of the acetoacetyl group in 100 of the wholemonomers is 5-100 mmoles. When it is less than 5 mmoles, numbers of thefine gel particles necessary for matting is insufficient while, when itis more than 100 mmoles, evenness of the resulting coated film isinsufficient.

(A)(1)(b). Common examples of the α,β-ethylenic unsaturated monomerhaving an acidic group are methacrylic acid and acrylic acid. Maleicacid, maleic acid anhydride, fumaric acid, itaconic acid, etc. may beused as well. Further examples which are applicable are the monomershaving an acidic group other than a carboxyl group such as acrylamidetert-butylsulfanic acid represented by the following formula 2! ##STR2##and mono(2-acryloyloxyethyl)acid phosphate represened by the followingformula 3!. ##STR3##

Those monomers having acidic groups may be used either solely or jointlyif necessary although it is necessary that an acid value of 10-200 (mgKOH/g solid in the resin) is achieved.

When it is less than 10 (mg KOH/g resin solid), stability of thedispersion in water after neutralization with the amine is insufficientwhile, when it is more than 200 (mg KOH/g resin solid), theelectrophoreticity is poor and, in addition, the property such as alkaliresistance is deteriorated.

(A)(1)(c) is a monomer which is polymerizable with the above-mentioned(a) and (b) and its examples are as follows. Although thoseα,β-ethylenic unsaturated monomers may be suitably selected dependingupon the requested quality such as hardness, softness, weatheringresistance, etc., it is advisable that the monomer having a hydroxylgroup is used within a range of 30-230 (mg KOH/g resin solid) of ahydroxyl value as a functional group upon curing and condensation in abaking step. When the hydroxyl value is less than 30, sufficientcrosslinking is not achieved while, when it is more than 230, waterresistance is poor and a satisfactory film property is not achieved.

Examples of those α,β-ethylenic unsaturated monomers are aromatic vinylmonomers such as styrene and vinyltoluene; alkyl acrylates ormethacrylates such as methyl acrylate, ethyl acrylate, butyl acrylate,hexyl acrylate, cyclohexyl acrylate, methyl methacrylatfe and ethylmethacrylate and derivatives thereof; amide compounds of acrylic acid ormethacrylic acid and derivatives thereof; and acrylonitile,methacrylonitrile, etc. If necessary, polyfunctional monomers such asdivinylbenzene and trimethylolpropane tri(meth)acrylate may be used aswell.

Examples of the α,β-ethylenic unsaturated monomers containing a hydroxylgroup are 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,2-hydroxypropyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate as wellas modified products thereof with a lactone.

Suitable examples of the α,β-ethylenic unsaturated monomers having anacidic group as mentioned in (A)(2)(a) are the same as those exemplifiedin the above (1)(b). The same thing is applied to the acid value too.

Examples of the α,β-ethylenic unsaturated monomers having a hydroxylgroup as mentioned in (A)(2)(b) are 2-hydroxyethyl (meth)acrylate,2-hydroxypropyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate as wellas the products modified with a lactone as mentioned already.

With respect to the hydroxyl value, 30-230 (mg KOH/g resin solid) issuitable the same as before but the hydroxyl value which is consumed byan acetoacetylation is to be previously considered to be outside 30-230(mg KOH/g resin solid).

(A)(2)(c) is a monomer which is polymerizable with the monomers of(2)(a) and (b) and its examples are the aromatic vinyl monomers, alkyl(meth)acrylates including derivatives thereof and (meth)acrylic acidamides incuding derivatives thereof. Polyfunctional monomers such asdivinylbenzene and trimethylolpropane tri(meth)crylates may also be usedif necessary.

Methods for polymerizing the above-mentioned monomers of (A)(1)(a), (b)and (c) and also of (A)(2)(a), (b) and (c) may be known methods such assolution polymerization, emulsion polymerization and suspensionpolymerization and, in the case of (A)(2), a solution polymerization isparticularly preferred. The polyerization catalyst used therefor may besuitably selected from the known ones such as azo compounds (e.g.azobisisobutyronitrile) and peroxide compounds (e.g. benzoyl peroxide).

For keeping the good dispersibility of the resulting polymers in water,it is useful to add alcohols such as ethanol, propanol and butanol andglycol ethers such as ethylene glycol monobutyl ether and ethyleneglycol dimethyl ether.

With respect to the solvent used for acetoacetylation of (A)(2), asolvent which is inert to the acetoacetylation should be selected.

The substance of (A)(2)(d) is a compound for conducting anacetoacetylation of the hydroxyl groups of the resin synthesized by(2)(a), (b) and (c) using diketene or acetoacetyl esters.

Examples of such a compound are methyl acetoacetate represented by thefollowing formula 4! ##STR4## ethyl acetoacetate represented by thefollowing formula 5! ##STR5## and tert-butyl acetoacetate represented bythe following formula 6! ##STR6##

The resulting anionic acryl resin containing acetoacetyl groups in theside chain prepared as such may be subjected to the followingneutralization and dilution with water after, if necessary, mixing withamino resin, xylene resin, epoxy resin, polyester resin, etc. dependingupon the requested property, workability, cost, etc. Further, mixingwith such a miscible resin may be utilized, if necessary, after theneutralization and dilution with water.

The amine (B) is to make the component (A) dispersible or soluble inwater by neutralization and its examples are alkyl or alkanolamines suchas monoethylamine, diethylamine, triethylamine, diethanolamine anddiisopropanolamine. Other examples are cyclic amines such as pyridineand ammonia. In some cases, inorganic alkali such as KOH and NaOH may beused. Useful degree of neutralization is 0.3-1.5 equivalents to saidcarboxylic acid. When it is less than 0.3 equivalent, the dispersing inwater is difficult while, when it is more than 1.5 equivalents, theelectrophoreticity is poor and that is not preferred.

It is preferred that the water used here is a deionized water. The useof deionized water which is previously mixed with a predetermined amountof the above-mentioned amine is a useful means as well.

A method in which a resin solution is poured into an aqueous amine, amethod in which a neutralized resin is poured into water, etc. may besuitably used too.

The higher the degree of neutralization with the amine or the higher thedegree of dilution with a deionized water, the finer the particle sizeof the resulting gel particles. Anionic and nonionic surface-activeagents may be added, if necessary, for controlling the particle size orfor achieving a stable dispersion.

Then an explanation will be made for the aldehyde. The resin particleswhich aree dispersed in water by the components (A) and (B) arecrosslinkingly condensed with the aldehyde which is the component (C) toproduce fine gel particles. Examples of the useful aldehyde are formalinand formalin condensates such as paraform. Besides those, aliphaticaldehydes such as acetaldehyde, propionaldehyde and butyraldehyde,aromatic aldehydes such as benzaldehyde and aldehyde condensates such asglyoxal may be used as well. The aldehyde is recommended to add in anamount of 0.1-10 moles, preferably 0.2-2 moles, to one mole of theabovementioned acetoacetyl group.

Alkoxylated methylolmelamine resin (D) having a water dilutability ofnot more than 4.0 cc will be explained in detail. The water dilutabilityis measured as follows. The sample (5 g) and 5 g of isopropanol whichare weighed by an even balance are mixed in a 100 ml beaker, water isdropped thereinto from a burette by keeping the temperature at 25° C.with stirring and the volume (milliliters) of water used for causing aturbidity is defined as the cc number of the water dilutability. Theendpoint of dropping is a stage when the printed letters (No.4 type)under the beaker are no longer able to be read. The alkoxylatedmethylolmelamine with a low water dilutability can be manufactured byconventional methods and can be obtained by a higher alkoxylation or bymaking the degree of condensation higher. Thus, in an industry, melamineresin by mixing methanol and butanol is used for electrodeposition andcan be manufactured by making the ratio of butanol higher. It can bemanufactured by adjusting the degree of polymerization higher by thecondensation of the melamine resin per se.

A crosslinking reaction takes place between the melamine resin and thehydroxyl groups of the above-mentioned component (A). In some cases, theresin with a water dilutability of more than 4 cc may be jointly used ifnecessary.

It is suitable to use 10-100 parts of the melamine resin with a waterdilutability of not more than 4 cc to 100 parts by weight of thecomponent (A). When it is less than 10 parts by weight, a sufficientcrosslinkingly coated film is not obtained while, when it is more than100 parts by weight, amount of the melanine resin is too much whereby asufficient crosslinking coated film is not obtained as well and,further, washing ability after the electrodesposition with water islowered in the electrodeposition operation.

The function of the alkoxylated methylolmelamine (D) with a waterdilutability of not more than 4.0 cc is believed to be as follows.

When water for washing is not uniformly present on the surface of theelectrodeposited coated film after washing with water in the course ofthe steps of electrodeposition-washing-baking, a speed of rising thetemperature of the thing to be coated in the baking furnace is retardedand, in some cases, luster and external appearance of the final coatedfilm after baking are no good since the etching effect of the area inwhich water is present is different from that in which no water ispresent. Especially in an industry, the water used for washing is afiltrate through UF membrane or RO membrane and contains water-solublesubstances and amines and, therefore, the abovementioned inconvenienceis apt to occur in an industry. Now, the melamine resin with a waterdilutability of not more than 4.0 cc is not soluble in water but iswater-repulsive and, accordingly, said resin is necessary for solvingsuch an inconvenience. Such a function cannot be expected by a melamineresin with a water dilutability of more than 4 cc.

Then, an acidic compound (E) with pKa of not more than 1.9 will beexplained as hereunder.

The acidic compound with pKa of not more than 1.9 is not alwaysessential when a crosslinking between the alkoxylated methylol melamine(D) with a water dilutability of not more than 4.0 cc and the anionicacrylresin (A) containing an acetoacetyl group in the side chain isconducted at an industrially common baking temperature, i.e. at nothigher than 180° C. However, because of a requirement for conservationof energy in recent years, there is a demand for achieving a good filmproperty at the baking temperature of a low region (e.g. at 150° C.)and, in such a case, the acidic compound with a pKa of not more than 1.9will be essential. At the baking temperature of such a low temperatureregion, an acidic compound with a pKa of more than 1.9 does not achievea good property of the coated film. Its suitable amount to 100 parts byweight of (A) is 0.1-2 parts by weight. The acidic compound which isevaporated during the baking is not effective and the use of thesulfonic acid catalyst is most useful. Reprentative examples arearomatic sulfonic acids such as p-toluenesulfonic acid. More specificexamples are monosulfonic acid such as p-dodecylbenzenesulfonic acid anddisulfonic acids such as dihexylnaphthalenedisulfonic acid. The use ofsuch an acidic compound in a form of a salt by neutralizing with theamine or the use of it after esterifying with a low-molecular epoxyresin or a lower alcohol, i.e. the use of it in a so-called maskedstate, is meaningful too.

In preparing a fine gel from such a formulation of the presentinvention, it is necessary to age it under the following condition. Sucha condition is to be suitably selected but the condition of stirring bycommon means at the temperature of 5°-100° C. for 5 minutes to 48 hours(preferably, at 20°-100° C. for 30 minutes to 3 hours) is advantagenousin an industrial scale.

The matted electrodeposition coating composition of the presentinvention containing the above-mentined components (A) to (D) and (E)may, if necessary, be diluted with deionized water or a solvent mainlycomprising water and then a predetermined voltage is loaded using thething to be coated as an anode to give an electrodeposition coated film.If necessary, it may be washed by common method. After that, it issubjected to a baking step to give a matted coated film.

EXAMPLES

The present invention will be further illustrated by the followingexamples.

Manufacturing Example of Anionic Acryl Resin (a-1) containingAcetoacetyl Groups in Side Chains.

A reaction apparatus equipped with stirring device, thermometer, devicefor dropping the monomers and reflux condenser was prepared.

    ______________________________________                                        (1)    Ethylene glycol monobutyl ether                                                                  25.0 parts by weight                                (2)    Isopropyl alcohol  50.0 parts by weight                                (3)    Ethylene glycol dimethacrylate                                                                    0.2 part by weight                                 (4)    n-Butyl acrylate   15.4 parts by weight                                (5)    Methyl methacrylate                                                                              25.6 parts by weight                                (6)    Styrene            30.0 parts by weight                                (7)    2-Hydroxyethyl acrylate                                                                          20.0 parts by weight                                (8)    Acetoacetoxyethyl methacrylate                                                                    2.4 parts by weight                                (9)    Acrylic acid        6.4 parts by weight                                (10)   Azobisisobutyronitrile                                                                            1.0 part by weight                                 (11)   Azobisisobutyronitrile                                                                            0.2 part by weight                                 ______________________________________                                    

(1) and (2) were charged in the reaction apparatus, heated up to arefluxing temperature with stirring and (3)-(10) which werehomogeneously mixed previously were dropped thereinto during threehours. The temperature was kept at 90°±3° C. After 1.5 hours sincecompletion of the dropping, (11) was added thereto. The reaction wascontinued at 90°±3° C. for 1.5 hours followed by cooling.

Transparent and viscous resin solution with a resin solid content of56.5% and an acid value of 52 mg KOH/g resin solid was obtained.

Manufacturing Example of Anionic Acryl Resin (a-2) containingAcetoacetyl Groups in Side Chains.

A reaction apparatus equipped with stirring device, thermometer, devicefor dropping the monomers and reflux condenser was prepared.

    ______________________________________                                        (1)    Diethylene glycol dimethyl ether                                                                 75.0 parts by weight                                (2)    Ethylene glycol dimethacrylate                                                                    0.2 part by weight                                 (3)    n-Butyl acrylate   15.4 parts by weight                                (4)    Methyl methacrylate                                                                              25.6 parts by weight                                (5)    Styrene            30.0 parts by weight                                (6)    2-Hydroxyethyl acrylate                                                                          21.3 parts by weight                                (7)    Acrylic acid        6.4 parts by weight                                (8)    Azobisisobutyronitrile                                                                            1.0 part by weight                                 (9)    Azobisisobutyronitrile                                                                            0.2 part by weight                                 (10)   tert-Butyl acetoacetate                                                                           1.8 parts by weight                                ______________________________________                                    

(1) was charged in a reaction apparatus, the temperature was raised upto 90° C. with stirring and (2)-(8) which were homogeneously mixedpreviously were dropped thereinto during three hours. The temperature atthat time was kept at 90°±3° C. After 1.5 hours since the completion ofthe dropping, (9) was added, the reaction was continued at 90°±3° C. for1.5 hours, the temperature was raised to 135° C., (10) was added, themixture was kept at 135°±3° C. for two hours, tert-butanol wasevaporated therefrom and the residue was cooled.

A transparent and viscous resin solution with a resin solid content of56.3% and an acid value of 50 mg KOH/g resin solid was obtained.

Manufacturing Example of Anionic Acryl Resin (a-3) containing noAcetoacetyl Group in Side Chains.

Resin was manufactured from the following formulation using the sameapparatus and procedures as in the case of (a-1).

    ______________________________________                                        (1)    Ethylene glycol monobutyl ether                                                                  25.0 parts by weight                                (2)    Isopropyl alcohol  50.0 parts by weight                                (3)    Ethylene glycol dimethacrylate                                                                    0.2 part by weight                                 (4)    n-Butyl acrylate   15.4 parts by weight                                (5)    Methyl methacrylate                                                                              25.6 parts by weight                                (6)    Styrene            30.0 parts by weight                                (7)    2-Hydroxyethyl acrylate                                                                          22.4 parts by weight                                (8)    Acrylic acid        6.4 parts by weight                                (9)    Azobisisobutyronitrile                                                                            1.0 part by weight                                 (10)   Azobisisobutyronitrile                                                                            0.2 part by weight                                 ______________________________________                                    

A transparent and viscous resin solution with a resin solid content of56.6% and an acid value of 50 mg KOH/g resin solid was obtained.

Example 1. Manufacturing Example of Matted Electrodeposition CoatingLiquid.

    ______________________________________                                        (1)  Resin solution of (a-1)                                                                            176.2 parts by weight                               (2)  Triethylamine         7.2 parts by weight                                (3)  Deionized water      160.0 parts by weight                               (4)  Alkoxylated methylolmelamine resin                                                                  30.0 parts by weight                                    (Sumimal M-8B; manu-                                                          factured by Sumitomo Chemical)                                           (5)  Formalin (35% aq formaldehyde soln)                                                                 0.4 part by weight                                 (6)  Deionized water      300.0 parts by weight                               (7)  Deionized water      951.2 parts by weight                               ______________________________________                                    

Water dilutability of Sumimal M-8B used here was 2.6 cc.

(2), (3) and (4) were added to (1) of 30° C. with stirring, the mixturewas stirred for one hour until it became homogeneous, (5) was addedthereto and the mixture was raised up to 80° C., stirred for two hoursmore and cooled. Then (6) and (7) were added thereto to give anelectrodeposition coating bath liquid.

A turbid electrodeposition coating bath liquid of 22° C. with a resinsolid content of 8%, pH of 9.1 and a specific resistance of 185 Ω.cm wasobtained.

(An Example of Electrodeposition Coating Process and Confirmation ofFine Gel Particles)

The resulting electrodeposition coating bath liquid was charged in athree-liter vessel made of polyvinyl chloride. SUS-304 was used as acathode while the anode (the thing to be coated) was a plate of 6063aluminum alloy which was anodically oxidized (thickness of the oxidizedcoat: 9 μm), electrolytically colored in black and rinsed with warmwater by a usual manner. The bath temperature, the polar distance andthe polar ratio (+/-) were made 22° C., 12 cm and 2/1, respectively andelectricity was loaded at 170 volts to give 10 μ by a usual method. Thiswas rinsed and baked and dried at 180° C. for 30 minutes.

The results are given in Table 1.

Examples 2-5.

    ______________________________________                                        (1)  Resin liquid of (a-1)                                                                              176.2 parts by weight                               (2)  Triethylamine         7.2 parts by weight                                (3)  Deionized water      160.0 parts by weight                               (4)  Alkoxylated methylolmelamine resin                                                                  30.0 parts by weight                                    (Sumimal M-8B manu-                                                           factured by Sumitomo Chemical)                                           (5)  Formalin (35% aq formaldehyde soln)                                                                 0.4 part by weight                                 (6)  Acidic compound (Catalyst 600 manu-                                                                 0.5 part by weight                                      factured by Mitsui                                                            Cytech KK)                                                               (7)  Deionized water      299.5 parts by weight                               (8)  Deionized water      951.2 parts by weight                               ______________________________________                                    

The Catalyst 600 used here was an aromatic sulfonic acid with a pKaof<1.0.

(2), (3) and (4) were charged to (1) of 30° C. with stirring, themixture was stirred for one hour until it became homogeneous, (5) wasadded thereto and the mixture was raised up to 80° C., stirred for twohours more and cooled. After that, (6), (7) and (8) were added to givean electrodeposition coating bath liquid.

A turbid electrodeposition coating bath liquid with a temperature of 22°C., a resin solid content of 8%, pH of 9.0 and a specific resistance of1,800 Ω.cm was obtained.

Examples of electrodeposition coating process and confirmations of finegel particles were conducted by the same manner as in Example 1 exceptthat the baking and drying operations were conducted at 150° C. for 30minutes.

Comparative Examples 1-6.

Using the formulations as shown in Table 2, the electrodepositioncoating bath liquids containing 8% of solid were prepared by the samemanner as in Example 1 followed by electrodeposition and baking.

The results are given in Table 2.

                  TABLE 1                                                         ______________________________________                                                     Examples                                                                      1    2      3      4    5    6                                   ______________________________________                                        Formulation (parts by weight)                                                 (A) Anionic Acryl Resin                                                           (a-1)          176.2       176.2                                                                              176.2                                                                              176.2                                                                              176.2                               (a-2)                 176.9                                               (B) Amine                                                                         (Triethylamine)                                                                              7.2    7.2       7.2  7.2  7.2                                 (Dimethylethanolamine)     7.2                                            (C) Aldehyde                                                                      (35% Aq Formaldehyde                                                                         0.4    0.4  0.4       0.4  0.4                                 Soln)                                                                         (35% Aq Glyoxal Soln)           0.4                                       (D) Melamine Resin                                                                (Sumimal M-8B) 30.0   30.0 30.0 30.0      30.0                                (Cymel #238) *1                      30.0                                 (E) Acidic Compound                           0.5                                 (Catalyst 600)                                                            Properties of the Bath                                                        Dissolution in Acetone *2                                                                    turb   turb   turb turb turb turb                              Particle Size (nm) *3                                                                        230    190    150  210  230  210                               Properties of the Coated Film                                                 Baking Temperature (C.°)                                                              180    180    180  180  180  150                               Baking Time (minutes)                                                                        30     30     30   30   30   30                                Film Thickness (μm)                                                                       10     10     11   10   9    10                                External Appearance                                                                          good   good   good good good good                              Gloss (60° Mirror Re-                                                                 28     30     35   29   27   28                                flectivity)                                                                   Pencil Hardness                                                                              4H     4H     4H   4H   4H   4H                                Resist. to Boiling Water *4                                                                  AR     AR     AR   AR   AR   AR                                Adhesion (1 × 1 mm)                                                                    #      #      #    #    #    #                                 CASS Test (48 hrs)                                                                           10.0   10.0   10.0 10.0 10.0 10.0                              Alkali Resistance (24 hrs)                                                                   10.0   10.0   10.0 10.0 10.0 10.0                              ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                                     Comparative Examples                                                          1    2      3      4    5    6                                   ______________________________________                                        Formulation (parts by weight)                                                 (A) Anionic Acryl Resin                                                           (a-1)                 176.2                                                                              176.2                                                                              176.2                                                                              176.2                                                                              176.2                               (a-3)          176.2                                                      (B) Amine          7.2         7.2  7.2  7.2  7.2                                 (Triethylamine)                                                           (C) Aldehyde       0.4    0.4       0.4  0.4  0.4                                 (35% Aq Formaldehyde                                                          Soln)                                                                     (D) Melamine Resin                                                                (Sumimal M-8B) 30.0   30.0 30.0      30.0 30.0                                (Nikalac MX-40) *5              30.0                                      (E) Acidic Compound                      0.5                                      (Catalyst 296-9) *6                                                       Properties of the Bath                                                        Dissolution in Acetone *2                                                                    clar   |      clar turb turb turb                              Particle Size (nm) *3                                                                        200    |      210  170  230  220                               Properties of the Coated Film                                                 Baking Temperature (C.°)                                                              180    |      180  180  150  150                               Baking Time (minutes)                                                                        30     |      30   30   30   30                                Film Thickness (μm)                                                                       10     |      10   11   10   9                                 External Appearance                                                                          good   |      good good good good                              Gloss (60° Mirror Re-                                                                 82     |      76   45   29   28                                flectivity)                                                                   Pencil Hardness                                                                              4H     |      4H   4H   2H   3H                                Resistance to Boiling                                                                        AR     |      AR   AR   AR   AR                                Water *4                                                                      Adhesion (1 × 1 mm)                                                                    #      |      #    #    #    #                                 CASS Test (48 hrs)                                                                           10.0   |      10.0 10.0 9.5  9.8                               Alkali Resistance (24 hrs)                                                                   10.0   |      10.0 10.0 9.8  10.0                              ______________________________________                                         turb: turbidity maintained                                                    clar: became clear                                                            AR: all right                                                                 #: 100/100                                                                    |: Due to aggregation, an electrodeposition coating was not possible.         *1: Cymel #236 (manufactured by Mitsui Cytech KK) with a water                dilutability of 2.4 cc                                                        *2: Deionized water (6) and (7) was added in Examples 1 and 6,                respectively and, after that, 100 g of acetone was added to 10 g of the       sample and the changes in turbidity was checked by naked eye.                 *3: Measured by an LPA3000/3100 manufactured by Otsuka Denshi KK.             *4: External appearance of the coated film after allowing to stand at         98° C. for five hours.                                                 *5: Nikalac MX40 (manufactured by Sanwa Chemical KK) with a water             dilutability of 4.7 cc.                                                       *6: Catalyst 2969 (manufactured by Mitsui Cytech KK) which is an acidic       catalyst of a phosphate type with a pKa of more than 1.9.                

MERIT OF THE INVENTION

In accordance with a composition of the present invention, fine gelparticles which are transparent, do not deteriorate the metallic feel ofthe undercoat and form fine unevenness can be prepared in water which isessential in a common electrodeposition process without a compulsory andmechanical means for preparing the particles such as dispersing by meansof sand mill or ball mill. In addition, when the electrodepositioncoating is carried out using the composition of the present invention,said fine particles per se exhibit a good electrophoretic property andan excellent homogeneous dispersibility in an bath and, accordingly, itis possible to afford a matted electrodeposition coated film withuniform and good design.

What we claim is:
 1. A matted electrodeposition coating composition which is characterized in containing (A) an anionic acryl resin having an acetoacetyl group in a side chain; (B) an amine and water; (C) an aldehyde; and (D) an alkoxylated methylolmelamine resin having a water dilutability of not more than 4.0 cc.
 2. A matted electrodeposition coating composition which is characterized in containing (A) an anionic acryl resin having an acetoacetyl group in a side chain; (B) an amine and water; (C) an aldehyde; (D) an alkoxylated methylolmelamine resin having a water dilutability of not more than 4.0 cc; and (E) an acidic compound with pKa of not more than 1.9.
 3. A method of producing a matted electrodeposition coating, characterized in that, the coated film is prepared using the composition of claim 1 by means of an electrodeposition coating method.
 4. A method of producing a matted electrodeposition coating, characterized in that, the coated film is prepared using the composition of claim 2 by means of an electrodeposition coating method. 